How to check if Cloud Firestore data is cached?

Question

After some reading, I learned about isFromCache() of Cloud Firestore to check if the data is from the cache. However, I don't know how to use it and there is not much detail in the documentation on how to use it.

I use FirestoreRecyclerView and the following is my onViewCreated():

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    val recyclerView = view.firestoreRecyclerView

    val db = Firebase.firestore

    val query : Query = db.collectionGroup("fire")

    val options : FirestoreRecyclerOptions<FireModel> =
        FirestoreRecyclerOptions.Builder<FireModel>()
            .setQuery(query, FireModel::class.java)
            .build()

    adapter = object : FirestoreRecyclerAdapter<FireModel, FireViewHolder>(options) {

        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): FireViewHolder{

            val v : View = LayoutInflater.from(parent.context).inflate(R.layout.fire_cardview, parent, false)

            return FireViewHolder(v)
        }

        override fun onBindViewHolder(
            holder: FireViewHolder,
            position: Int,
            model: FireModel
        ) {
            holder.name.text = model.name.name
            holder.address.text = model.address.unitName
            holder.age.text = model.age.toString()
}


class FireViewHolder(v : View) : RecyclerView.ViewHolder (v) {

    var name : TextView = v.nameTextView
    var address: TextView = v.addressTextView
    var age: TextView = v.ageValueTextView
}

and my Model Class:

@Keep
@Parcelize
class FireModel (

    var name : String = "",
    var address : String = "",
    var age : Int = 0
) : Parcelable